Looking for ways oil can get into the water and water into the oil without a blown head gasket being the problum.

Having an issue with a freinds 390. This engine was completely rebuilt by me 4 years ago and installed into a "76 F-250 High-boy 4X4. This engine was built to '68 specs, balanced w/ 9to1 compression, punched .040. Crane RV cam advanced 2 degrees, low cc heads, high volumn oil pump, reworked oil galleys to improve oil flow, matchported Performer intake and heads, oversized exhaust valves with steel seats, with a reworked & tuned AFB on top with Hooker headers and several other little things I would do to race engines. Used all Fel-pro Blue-Line gaskets and Copper Coat on the head gaskets. For a street driver I did not build this to hot but I did want it to run and pull well. Mission accomplished.

My freind claims this engine begin exibiting oil in the water about 3 months ago. Then one day while he was driving to work about 65 mph at a steady rate up a slight incline he experianced a backfire, a sudden loss of power for a few seconds and a return of power with white smoke then appearing out the left exhaust pipe. He continued to drive it for about another 5 minutes to get to work and shut it off. We have not tried to start it since.

Once I found time to get it in my garage we commenced with checking the anti-freeze and for water in the oil. The radiator was about a gallon low and I ended up draining about a gallon of water out of the oil pan before oil appeared. Drained out the remaining oil and found no metal flake or bearing babbit in either the anti freeze or the oil so we assumed the crank and rods are ok. Finished rinsing out the engine with a oil / mineral spirits combinition to wash out the foam that results from an oil/water mixture out of the oil galleys and such.

Ran we a compression check to look for a weak cylinder or two and found the following; 156, 147, 141, 143, 132, 147, 151, 149. So naturally we thought the #5 hole w/ 132 was the issue with a leaky head gasket. So we commenced with tearing the engine down to remove the left head and upon removal we could not find anything the was evidant to leakage. The head gasket appeared to be intact with no obvious evidence of leakage. So we proceded to remove the right head and discovered it was in the same condition as the left.

OK, now we're stumped. Question is how did oil get in the water? And, How did water get in the oil?.

I investigated all the intake gaskets and they looked good but oil and water do not come close together where oil can get in the water .

I investigated the block while still in the vechicle and looked for evidance of a cracked cylinder and other than a little scoring I could not find anything that would indicate a cracked cylinder.

I also investigated the heads for a possible crack but without tearing them apart and hot-tanking them I have not been able to find a crack that is obvious.

So in closing I am lookin for any input as to how we got oil and water in the wrong places.

First thing that I would do is follow the water path. From the radiator, to the water pump, into the block, to the rear of the block, up to the head, back to the front of the head, then into the intake, and back to the radiator.

My suspitions lead to a fault in a gasket. If the the head gasket was instlled wrong you'll have problems. There is an opening on the gasket for water flow, and must be installed with the opening to the rear.

Another gasket problem is the intake gasket. Port maching and all that don't mean squat if you can't keep a seal between the head and the intake. So look for signs there also.

The backfiring could be any number of things.

Since you have the heads off do a preasure test to find out if the heads could be leaking water. Some times you can get close to the water jacket while porting and not even know it and it'll blow water through a small pinhole. Does the valves and pistons show signs of water by a film of dirt and or coolant, other than the residual water from removing the head?

The only real way to test for cracks in the block is a sonic test, that way you know for sure.

Was the head milled or the block decked? If so the intake might not of seated properly and that could cause problems.

You stated that you used felpro gaskets, I don't know why you would use copper seal. If you were using metal gaskets it would be understandable, point being, metal gasgets, even with copper coating will leak if the heads and block aren't machined perfectly straight and flat.

*Point of note* If you were definitly using coolant, and it mixed with the oil, more than likely your going to need to grind the crank install new bearings, and a new oil pump. By experiance.....coolant doesn't play well with the rotating assembly!